McLennan S V, Martell S K Y, Yue D K
Department of Endocrinology, Royal Prince Alfred Hospital, Sydney, NSW, Australia.
Diabetes. 2002 Aug;51(8):2612-8. doi: 10.2337/diabetes.51.8.2612.
High glucose concentrations can decrease degradation of mesangium by reducing the activities of matrix metalloproteinases (MMPs). The aim of this study was to investigate the effects of glycation of mesangium matrix on MMP-2, the principal MMP secreted by mesangial cells to degrade type IV collagen. Also examined were membrane type 1 MMP (MT1-MMP), tissue inhibitors of MMPs (TIMP)-1 and -2, and transforming growth factor-beta (TGF-beta), which together regulate MMP-2 activities in an interacting manner. Human fetal mesangial cells were grown on mesangium matrix glycated by incubation in 500 mmol/l ribose, with or without aminoguanidine. The activities and gene expression of the abovementioned enzymes/inhibitors were measured by degradation of radiolabeled mesangium matrix, RT-PCR, and zymography. Glycation of mesangium matrix resulted in a threefold increase in advance glycation end products and reduced by 45% the matrix-degrading activity of MMPs secreted by mesangial cells. Analogous to the direct effects of high glucose concentrations, glycation of matrix increased the gene expression of MMP-2 and TIMP-1 (control 100 +/- 16.9 vs. glycated 197.3 +/- 30.6% and control 100 +/- 5.3 vs. glycated 152.1 +/- 20.1%, respectively; P < 0.05) and decreased MT1-MMP (control 100 +/- 1.17 vs. glycated 54.1 +/- 15.2%; P < 0.05). However, unlike high glucose concentrations, glycation was not associated with decreased activation of MMP-2. Similarly, glycation but not high glucose increased expression of TIMP-2 (control 100 +/- 5.9 vs. glycated 168.2 +/- 31.4%; P < 0.05), and the effects of glycation on degradation can be abolished by anti-TIMP-2 antibody. Glycation of matrix decreased TGF-beta mRNA by 38.2% and total and active TGF-beta by 35.5 and 21.5%, respectively, opposite the effects of high glucose concentrations. Our results indicate that glycation of matrix affects the balance between MMP-2 and its activator and inhibitors, but this phenomenon is not due to TGF-beta. The process of glycation may impart to the mesangium matrix a memory effect that contributes to the long-term toxicity of hyperglycemia.
高糖浓度可通过降低基质金属蛋白酶（MMPs）的活性来减少肾小球系膜的降解。本研究的目的是探讨肾小球系膜基质糖基化对MMP-2的影响，MMP-2是系膜细胞分泌的主要MMP，可降解IV型胶原。同时还检测了膜型1 MMP（MT1-MMP）、MMP组织抑制剂（TIMP）-1和-2以及转化生长因子-β（TGF-β），它们共同以相互作用的方式调节MMP-2的活性。将人胎儿系膜细胞培养在通过在500 mmol/l核糖中孵育而糖基化的系膜基质上，添加或不添加氨基胍。通过放射性标记的系膜基质降解、逆转录聚合酶链反应（RT-PCR）和酶谱法测量上述酶/抑制剂的活性和基因表达。系膜基质糖基化导致晚期糖基化终产物增加三倍，并使系膜细胞分泌的MMPs的基质降解活性降低45%。与高糖浓度的直接影响类似，基质糖基化增加了MMP-2和TIMP-1的基因表达（对照组分别为100±16.9 vs.糖基化组197.3±30.6%，对照组100±5.3 vs.糖基化组152.1±20.1%；P<0.05），并降低了MT1-MMP（对照组100±1.17 vs.糖基化组54.1±15.2%；P<0.05）。然而，与高糖浓度不同，糖基化与MMP-2的活化降低无关。同样，糖基化而非高糖增加了TIMP-2的表达（对照组100±5.9 vs.糖基化组168.2±31.4%；P<0.05），并且糖基化对降解的影响可被抗TIMP-2抗体消除。基质糖基化使TGF-β mRNA降低38.2%，使总TGF-β和活性TGF-β分别降低35.5%和21.5%，与高糖浓度的影响相反。我们的结果表明，基质糖基化影响MMP-2与其激活剂和抑制剂之间的平衡，但这种现象不是由TGF-β引起的。糖基化过程可能赋予系膜基质一种记忆效应，这有助于高血糖的长期毒性作用。
